Hello, I Am Suffering From Achnae Valgaris For That Dermatologist

Hello, I am suffering from Achnae valgaris for that dermatologist prescribed me isotretinoin capsule(10mg) and neurobin tab. During d intake of this medicine I had intercourse so I taken contraceptive(I pill) after taking that my bleeding started I concern a gynaecologist they said it use to happen so better I take precautions next time but on next month as my cycle date is here I am worried as it's not starting I did pregnancy test its negative what could be the reason and what will be the treatment.